add onions, small onions, tomatoes, salt, turmeric powder, drumstick and water. mix well, close and cook until drumstick is cooked.
heat oil in a pan and roast cumin seeds, coriander seeds, chana dal, urad dal, asafoetida, peppercorns and fry for few seconds until slightly reddish
further add red chillies, curry leaves, grated coconut and fry till reddish.
add jaggery and tamarind. let it cool and grind finely.
fry the masala till it starts changing colour.
add the masala, cooked and mashed tur dal, adjust salt and add water.
mix well, close and let it boil for 10 minutes.
heat oil for tempering. crackle mustard seeds, curry leaves and add the tempering to the sambar.